The Boundary Treaty of 1881 was a significant diplomatic agreement that defined the border between Chile and Argentina, primarily in the disputed regions of Patagonia. The treaty was signed in Buenos Aires after prolonged negotiations aimed at clarifying territorial claims that had resulted in tensions between the two South American nations. The key negotiators included Chilean Foreign Minister Federico Errázuriz and Argentine Minister of Foreign Affairs Miguel Juárez Celman, who worked tirelessly to reach a consensus that would benefit both countries while minimizing conflict. The discussions also reflected broader regional dynamics, including the influence of other neighboring countries and international pressures to maintain peace in South America.

The treaty's stipulations were grounded in a combination of geographical features and political considerations, targeting specific natural landmarks as border markers. This agreement provided a framework for future relations and disputes, as well as established protocols for territorial governance. The signing of this treaty not only facilitated an end to the border conflicts that had emerged in the previous decades but also served as a precedent for how such disputes could be settled diplomatically.

As a result of the treaty, both nations underwent periods of territorial consolidation, with Argentina extending its claims further into Patagonia while Chile affirmed its sovereignty over crucial areas. The implications of this agreement continued to resonate in Chilean and Argentine geopolitics, influencing subsequent discussions on trade, migration, and environmental management in these frontier regions.